Monthly Notices of the Royal Astronomical Society, 353, 1107-11167 (2004)

We apply the sky brightness modelling technique introduced and developed by Roy
Garstang to high-resolution satellite measurements of upward artificial light
flux carried out with the US Air Force Defense Meteorological Satellite Program
Operational Linescan System and to GTOPO30 (a global digital elevation model by
the US Geological Survey’s EROS Data Centre) digital elevation data in order
to predict the brightness distribution of the night sky at a given site in the
primary astronomical photometric bands for a range of atmospheric aerosol
contents. This method, based on global data and accounting for elevation, Earth
curvature and mountain screening, allows the evaluation of sky glow conditions
over the entire sky for any site in the world, to evaluate its evolution, to
disentangle the contribution of individual sources in the surrounding territory
and to identify the main contributing sources. Sky brightness, naked eye stellar
visibility and telescope limiting magnitude are produced as three-dimensional
arrays, the axes of which are the position on the sky and the atmospheric
clarity. We compare our results with available measurements.

Monthly Notices of the Royal Astronomical Society, 328, 689-707 (2001)

We present the first World Atlas of the zenith artificial night sky brightness
at sea level. Based on radiance calibrated high resolution DMSP satellite data
and on accurate modelling of light propagation in the atmosphere, it provides
a nearly global picture of how mankind is proceeding to envelope itself in a
luminous fog. Comparing the Atlas with the U.S. Department of Energy (DOE)
population density database we determined the fraction of population who are
living under a sky of given brightness. About two thirds of the World
population and 99% of the population in US (excluding Alaska and Hawaii) and
EU live in areas where the night sky is above the threshold set for polluted
status. Assuming average eye functionality, about one fifth of the World
population, more than two thirds of the US population and more than one half
of the EU population have already lost naked eye visibility of the Milky Way.
Finally, about one tenth of the World population, more than 40% of the US
population and one sixth of the EU population no longer view the heavens with
the eye adapted to night vision because the sky brightness.

Moonlight
without the moon

Earth, Moon and Planets, 85-86, 517-522 (2001). not
available for download

Light pollution, the alteration of the natural light levels in the night
environment produced by man-made light, is one of the most rapidly increasing
threats to the natural environment. The fast growth of the night sky brightness
due to light pollution not only is damaging the perception of the starry sky but
it is silently altering even the perception of the moonlight nights by mankind.
The cyclic alternation between the new moon's dark sky with thousand of stars
and the moonlight sky, less dark but always full of stars among which our
satellite moves, is rapidly changing toward a perennial artificial moonlight due
to the man-made light wasted in the atmosphere. The moon periodically will
appear inside the same perennially luminous sky from which stars will be almost
disappeared. Here we present a map showing "artificial moonlight"
levels in North America and some statistical results.

Blinded by the light

New Scientist, 2304, 18 (18 August 2001) not
available for download

New Scientist presented a news about
our World Atlas of the sea level
artificial night sky brightness from Cinzano, P., Falchi, F.,
Elvidge 2001, Monthly Notices of the Royal
Astronomical Society, 328, 689-707.

We extend the method introduced by Cinzano et al. (2000a) to map the
artificial sky brightness in large territories from DMSP satellite data, in
order to map the naked eye star visibility and telescopic limiting magnitudes.
For these purposes we take into account the altitude of each land area from
GTOPO30 world elevation data, the natural sky brightness in the chosen sky
direction, based on Garstang modelling, the eye capability with naked eye or a
telescope, based on the Schaefer (1990) and Garstang (2000b) approach, and the
stellar extinction in the visual photometric band. For near zenith sky
directions we also take into account screening by terrain elevation. Maps of
naked eye star visibility and telescopic limiting magnitudes are useful to
quantify the capability of the population to perceive our Universe, to
evaluate the future evolution, to make cross correlations with statistical
parameters and to recognize areas where astronomical observations or
popularisation can still acceptably be made. We present, as an application,
maps of naked eye star visibility and total sky brightness in V band in Europe
at the zenith with a resolution of approximately 1 km.

Monthly Notices of the Royal Astronomical Society,
318, 641-657 (2000)

We present a method to map the artificial sky brightness across large
territories in astronomical photometric bands with a resolution of
approximately 1 km. This is useful to quantify the situation of night sky
pollution, to recognize potential astronomical sites and to allow future
monitoring of trends. The artificial sky brightness present in the chosen
direction at a given position on the Earth's surface is obtained by the
integration of the contributions produced by every surface area in the
surrounding. Each contribution is computed based on detailed models for the
propagation in the atmosphere of the upward light flux emitted by the area.
The light flux is measured with top of atmosphere radiometric observations
made by the Defense Meteorological Satellite Program (DMSP) Operational
Linescan System.
We applied the described method to Europe obtaining the maps of artificial sky
brightness in V and B bands.

in Preserving the Astronomical Sky, IAU Symposium 196, Cohen R.J.
& Sullivan W.T. (eds.), ASP Conf. Series, 95-102 (2001). Proceedings of the
Symposium held in the United Nations Vienna International Conference Centre in
conjunction with UNISPACE II (12-16 July 1999).

We present the map of the artificial sky brightness in Europe in V band with a
resolution of approximately 1 km. The aim is to understand the state of night
sky pollution in Europe, to quantify the present situation and to allow future
monitoring of trends.
The artificial sky brightness in each site at a given position on the sky is
obtained by integration of the contributions produced by every surface area in
the surroundings of the site. Each contribution is computed taking into
account based on detailed models the propagation in the atmosphere of the
upward light flux emitted by the area and measured by the Operational Linescan
System of DMSP satellites. The modelling technique, introduced and developed
by Garstang and also applied by Cinzano, takes into account the extinction
along light paths, a double scattering of light from atmospheric molecules and
aerosols, Earth curvature and allows to associate the predictions to the
aerosol content of the atmosphere.

Mapping the artificial
sky brightness in Europe from DMSP satellite measurements: the situation of the
night sky in Italy in the last quarter of century

We present a project to map the artificial sky brightness in Europe in the
main astronomical photometrical bands with a resolution better than 3 km. The
aim is to understand the state of night sky pollution in Europe, to quantify
the present situation and to allow future monitoring of trends. The artificial
sky brightness in each site at a given position on the sky is obtained by the
integration of the contributions produced by every surface area in the
surroundings of the site. Each contribution is computed taking in account the
propagation in the atmosphere of the upward light flux emitted by the area and
measured from DMSP satellites. The project is a long term study in which we
plan to take in account successively of many different details in order to
improve the maps. We present, as a preliminary result, a map of the V-band
artificial sky brightness in Italy in 1998 and we compare it with the map
obtained 27 years earlier by Bertiau, Treanor and De Graeve. Predictions for
the artificial sky brightness within the next 27 years are also shown.

The Propagation of Light
Pollution in Diffusely Urbanised Areas

The knowledge of the contribution b_d(d) to the artificial sky luminance in a
given point of the sky of a site produced by the sources beyond a given
distance d from it is important to understand the behaviour of light pollution
in diffusely urbanized areas and to estimate which fraction of the artificial
luminance would be regulated by norms or laws limiting the light wasted upward
within protection areas of given radii.
I studied the behaviour of b_d(d) constructing a model for the propagation of
the light pollution based on the modelling technique introduced by Garstang
which allows to calculate the contribution to the artificial luminance in a
given point of the sky of a site of given altitude above sea level, produced
by a source of given emission and geographic position. I obtained b_d(d)
integrating the contribution to the artificial luminance from every source
situated at a distance greater than d. I also presented an analitical
expression for b_d(d) depending mainly from one parameter, a core radius, well
reproducing model's results.
In this paper I present the results for b_d(d) at some Italian Astronomical
Observatories. In a diffusely urbanised territory the artificial sky luminance
produced by sources located at large distances from the site is not negligible
due at the additive character of light pollution and its propagation at large
distances. Only when the core radius is small, e.g. for sites in the inner
outskirts of a city, the sky luminance from sources beyond few kilometers is
negligible. The radii of protection zones around Observatories needs to be
large in order that prescriptions limiting upward light be really effective.

The Artificial Sky
Luminance And The Emission Angles Of The Upward Light Flux

The direction of the upward light emission has different polluting effects on
the sky depending on the distance of the observation site. We studied with
detailed models for light pollution propagation the ratio b_H/b_L, at given
distances from a city, between the artificial sky luminance b_H produced by
its upward light emission between a given threshold angle \theta_0 and the
vertical and the artificial sky luminance b_L produced by its upward light
emission between the horizontal and the threshold angle theta_0. Our results
show that as the distance from the city increases the effects of the emission
at high angles above the horizontal decrease relative to the effects of
emission at lower angles above the horizontal. Outside some kilometers from
cities or towns the light emitted between the horizontal and 10 deg is as
important as the light emitted at all the other angles in producing the
artificial sky luminance. Therefore the protection of a site requires also a
careful control of this emission which needs to be reduced to at most 1/10 of
the remaining emission. The emission between the horizontal and 10deg is
mostly produced by spill light from luminaires, so fully shielded fixtures (e.g.
flat glass luminaires or asymmetric spot-lights installed without any tilt)
are needed for this purpose.

The growth of light pollution in North-Eastern Italy
from 1960-1995

I studied the growth rate of light pollution in the Veneto plain (Italy) analyzing archive measurements of sky brightness obtained in V, B and R bands at the Ekar Astronomical Observatory and at the Asiago Astronomical Observatory in the period 1960-1995. The light pollution in the last 35 years has increased exponentially. Assuming a constant annual increase from 1960 to 1995, the mean annual increase results of 10 percent per year. In the period 1990-1996 at the Observatory sites the strong increase of the artificial sky brightness was hidden by the decrease of the natural sky brightness due to the decrease of airglow emission produced by the sun activity going to its minimum but in the next 5 years the artificial sky brightness and the increasing airglow emission will sum producing a rapid growth of the sky
brightness.

Modelling light pollution from searchlights

I analyzed with a simple double scattering model
the artificial sky luminance produced by the light pollution coming from an advertising searchlight. I evaluated both the artificial luminance produced by direct illuminance of
atmospheric particles and molecules on the line-of-sight and that produced by light scattered once. I take in account the height above
sea level of the observing site and the orientation of the beam.

We obtained the map of the zenith brightness of the night sky in Italy. The
artificial sky brightness in each site is computed by integration of the
contributions by each unitary area of surface obtained by applying a
propagation function to the upward emission of the area as obtained from DMSP
satellite night-time images. We also evaluated the emission versus population
relationship comparing the relative emissions of a number of cities of various
populations.